Hydroxynaphthalenecarboxylic acid amide compounds are important compounds used for synthesizing a wide variety of materials, for example, organic dyes such as azo dyes, medical and agricultural chemicals. Such compounds are derived from hydroxynaphthalenecarboxylic acid compounds such as 2-hydroxy-6-naphthoic acid, 2-hydroxy-3-naphthoic acid and 2-hydroxynaphthalene-3,6-dicarboxylic acid.
A conventionally used method for producing a hydroxynaphthalenecarboxylic acid amide compound comprises amidating an acid halide of a hydroxynaphthalenecarboxylic acid compound with an amidating reagent such as ammonia gas and aqueous ammonia (see WO2005/012231, Japanese Patent Application Laid Open (Kokai) Nos. S62-120348 and S63-174963).
However, ammonia gas or aqueous ammonia may cause mucosal irritation and may develop rancid odor. Therefore, said method is not preferable in terms of the working environment. Further, ammonia gas has difficulties in handlings, such as controlling the gas flow rate, due to its gaseous properties. Furthermore, when the amidation step is performed by introducing ammonia gas into the reaction mixture, a hydroxynaphthoic acid amide compound, which is the reaction product, tends to be precipitated near the end of the gas introducing tube, which may result in the pipe blockage.
Another amidation method known to the art comprises amidating a hydroxynaphthalenecarboxylic acid compound with ammonium carbonate in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzothiazole using N,N-dimethylformamide as a solvent(see US-A-2005/0182091, Preparation 58).
However, the method disclosed in US-A-2005/0182091 is not industrially advantageous because it uses a large amount of expensive reagents such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzothiazole.
Accordingly, there is a demand for a method for producing a hydroxynaphthalenecarboxylic acid amide compound using an inexpensive amidating reagent which is less harmful to the working environment.